Urban plant ecology patterns and processes: a case study of the flora of the City of Plymouth, Devon, U. K.

Abstract

Summary AimUsing a large database that has been created over the past 5 years with the RECORDER package, presence/absence data for 829 species of vascular plants in the 103 1‐km2 squares that cover the city of Plymouth (pop. 243,373) have been analysed by two‐way indicator species analysis (TWINSPAN) and canonical correspondence analysis (CCA) to establish the major species assemblages and to examine their spatial distribution across the city in relation to variation in land use. LocationThe City of Plymouth. MethodsNine groupings of squares emerged and their distribution was mapped across the city. Interpretation of those groups and their variation in relation to the land use ordination axes showed that TWINSPAN groups lying along the first axis of variation correlated floristic variation with the process of urban development and the historical evolution of urban structure. The second axis appeared to be related to particular remnant semi‐natural habitats within the city that could be regarded as ‘hot‐spots’ for survival of many plant species. Species were categorized into four types on the basis of their recency and mode of arrival in the city and by using the historical flora of Plymouth produced by T. R. Archer‐Briggs in 1880. Variations in the sources of species in relation to the TWINSPAN classification groups were then examined. A second ordination was also computed; this time with geological, altitudinal and distance variables. TWINSPAN groups were then superimposed on the ordinations using polygons to assist with biogeographical interpretation. Results and conclusions The results of both the multivariate analyses and distribution of species by source are then discussed in the context of previous research into urban plant ecology, particularly in Central Europe. The problems of inferring process from pattern in this meso‐scale study are reviewed and suggestions are made for further research into urban ecology and biogeography in the city.

Arboricultural Introductions and Long-Term Changes for Invasive Woody Plants in Remnant Urban Forests

“…As expected from the literature on naturalization of alien species in cities [10][11][12][13][14][15][16][17][18][19][20], the number of invasive species significantly increased over the four time periods for the floras of the four cities and remnant urban forests. In sharp contrast, the correlation analysis did not provide support for the existence of a relationship between residence time and number of presences in floras as suggested by the literature from cities in Europe and Australia [16][17][18][19].…”

“…Comparisons of floras from different time periods have formed long-term datasets in biodiversity research to determine changes in the native and non-native components of urban floras in many countries. The research has focused on examining how arboricultural introductions relate to all alien species that have become naturalized in cities rather than only invasive species which cause large scale losses of native species in remnant urban forests [10][11][12][13][14][15]. Analysis of alien species naturalization has focused on residence time, which depends on the year of introduction to arboriculture, since the longer a species is present in cultivation the greater the opportunity for escape and establishment in the forests of a study region.…”

A meta‐analysis of the effects of urbanization on ground beetle communities

“…The relative sensitivity of predators, omnivores, and herbivores may also reflect differences in resource availability between rural and urban forests and may indicate that trophic processes are frequentv www.esajournals.org ly disrupted in cities (Faeth et al 2005). For example, weed seed availability is a good predictor of the distribution of herbivorous carabids in agricultural fields (Honěk andJarošík 2000, Saska 2004), and urban forests may have more weedy plants than do rural forests by nature of increased light penetration, disturbance, proximity of vacant lots, and the establishment of alien species (Crowe 1979, Pyšek 1998, Kent et al 1999, Duguay et al 2007, Luck and Smallbone 2010. Omnivores might be expected to exhibit little change in abundance along urbanization gradients due to their presumably more flexible feeding habits.…”

Socioeconomics drive urban plant diversity

“…To date, urban ecosystem characteristics have been evaluated largely in terms of the urban-to-rural gradient paradigm (10)(11)(12)(13), with the simple linear gradient concept evolving to include gradients of disturbance, land-use intensity, and the polycentric, anisotropic nature of modern cities (14,15). However, such studies typically focus on patches of native vegetation within cities (16)(17)(18)(19) rather than the full range of land-use types with their human-created plant communities that characterize much of the urban landscape. In addition, conceptual developments have identified the need to quantify gradients of resource availability and disturbance that integrate land use, legacy effects, socioeconomic status, and cultural differences, because these may mediate the human-environment interaction and influence resultant ecological conditions (20)(21)(22)(23)(24).…”